Method for manufacturing inkjet head

ABSTRACT

A method for manufacturing an inkjet head is disclosed. The method for manufacturing an inkjet head can include preparing a head body including a vibrating membrane, which is located in an upper portion of the head body, coating a lower electrode over the vibrating membrane, patterning a resist such that an open area is formed over the vibrating membrane, filling a piezoelectric material in the open area, selectively coating an upper electrode over the piezoelectric material, and removing the resist.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefits of Korean Patent Application Nos. 10-2009-0100364 and 10-2009-0107085, filed with the Korean Intellectual Property Office on Oct. 21, 2009 and Nov. 6, 2009, respectively, the disclosure of which is incorporated herein by reference in their entirety.

BACKGROUND

1. Technical Field

The present invention relates to a method for manufacturing an inkjet head.

2. Description of the Related Art

An inkjet head can be manufactured by processing various parts, such as the chamber, restrictor, nozzle, etc., in a number of layers and then attaching the layers together.

Generally, a piezoelectric device (PZT) is utilized to drive a vibrating membrane. When some voltages are provided to both sides of the piezoelectric device, an inner crystal structure of the piezoelectric device is changed and a displacement can be generated in the piezoelectric device. The operation of the vibrating membrane utilizes the displacement.

To keep pace with an increase of nozzle density of the inkjet head, the distance between unit cells for discharging ink droplets needs to be narrower, and the vibrating membrane and the piezoelectric device need to be thinner.

According to the prior art, in order to form a piezoelectric device for each cell, a lower electrode is deposited on a head body and a piezoelectric material is coated on the lower electrode with epoxy resin. Then the deposited piezoelectric material is separated in accordance with each cell by means of, for example, a blade. At this time, the vibrating membrane may be cracked when the lower electrode is contacted by the blade since the lower electrode is thin. Therefore, to prevent this, the piezoelectric material is separated into several piezoelectric devices such that a residue layer remains in the piezoelectric material.

The residue layer causes a cross talk that delivers the operating power of a piezoelectric device of one cell to another cell. This causes a defective discharging of ink.

SUMMARY

An aspect of the invention provides a method for manufacturing an inkjet head. The method in accordance with an embodiment of the present invention can include: preparing a head body including a vibrating membrane, which is located in an upper portion of the head body; coating a lower electrode over the vibrating membrane; patterning a resist such that an open area is formed over the vibrating membrane; filling a piezoelectric material in the open area; selectively coating an upper electrode over the piezoelectric material; and removing the resist.

Here, the resist can be made of a material including polysilicon, and the resist can be removed by an etching process using XeF2 gas.

Also, the method for manufacturing an inkjet head according to an embodiment of the invention can further include forming an inlet port in the head body, after the resist is removed.

The piezoelectric material can be filled by: depositing the piezoelectric material in the open area and over the resist; and removing a portion of the deposited piezoelectric material such that an upper surface of the resist is exposed.

Meanwhile, the resist can be a photo-resist, and the upper electrode can be selectively coated by: coating a conductive layer over the piezoelectric material and over the photo-resist; and patterning the upper electrode over the piezoelectric material by removing a portion of the conductive layer coated over the photo-resist by etching the photo-resist.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method for manufacturing an inkjet head according to an embodiment of the invention

FIGS. 2 to 11 illustrate a respective process of a method for manufacturing an inkjet head according to an embodiment of the invention.

FIGS. 12 and 13 illustrate a process for coating an upper electrode selectively according to another embodiment of the invention.

DETAILED DESCRIPTION

A method for manufacturing the inkjet head according to certain embodiments of the invention will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant descriptions are omitted.

FIG. 1 is a flowchart illustrating a method for manufacturing an inkjet head according to an embodiment of the invention, and FIGS. 2 to 10 illustrate a respective process of a method for manufacturing an inkjet head according to an embodiment of the invention.

First, as illustrated in FIG. 2, a head body 10, including a vibrating membrane 16, is prepared, and a lower electrode 20 is coated over the vibrating membrane 16 (S 110). The vibrating membrane 16 is located in an upper portion of the head body 10. For coating the lower electrode 20, gold can be deposited on an upper surface of the vibrating membrane 16, but the present invention is not limited to depositing gold.

In the head body 10, some elements such as a chamber 13, a reservoir 11, a restrictor 13, a damper 14, and a nozzle 15 are formed. Described below are the functions of the elements constituting the head body 10.

The chamber 13 accommodates ink. When a piezoelectric material (refer to reference numeral 42 in FIG. 11), which is formed on an upper surface of the vibrating membrane, applies pressure to the chamber 13, the chamber 13 transfers the accommodated ink in the direction of the nozzle 15 and causes the ink to be discharged. There can be a number of chambers, for example, 128 chambers, 256 chambers, etc., in parallel in one ink-jet head, and there can be an equal number of piezoelectric devices in order to provide pressure to each chamber 13.

The reservoir 11 is supplied with the ink from the outside through an inlet port 12 and stores the ink, and then provides the ink to the chamber 13 described above.

The restrictor 13 links the reservoir 11 and the chamber 13 and controls the ink flow generated between the reservoir 11 and the chamber 13. The restrictor 13 is formed to have a smaller cross sectional area than those of the reservoir 11 and the chamber 13. The restrictor 13 can control the amount of ink provided by the reservoir 11 to the chamber 13 when the vibrating membrane 16 is vibrated by a vibration generator.

The nozzle 15 is linked to the chamber 13 and is supplied with the ink from the chamber 13. Then, the ink is ejected through the nozzle. If the vibration generated by the vibration generator is delivered to the chamber 13 through the vibrating membrane 16, pressure is applied to the chamber 13, causing the ink to be ejected through the nozzle 15.

The damper 14 is formed between the chamber 13 and the nozzle 15. The damper 14 can carry out a function of converging the energy generated by the chamber 13 to the nozzle 15 and dampening a sudden change of pressure.

The head body 10 including the elements described above can be formed by stacking one or several substrates made of silicon or ceramic material.

Then, as shown in FIG. 3, a resist 30 is patterned such that an open area 32 is formed over the lower electrode 20 (S120). The open area 32 is an area in which a piezoelectric material (refer to reference numeral 42 in FIG. 11) is to be filled. The piezoelectric material 42 can later serve as a vibration generator. In this embodiment, the resist 30 is patterned by depositing polysilicon by using PECVD or LPCVD. However, the present invention is not limited to patterning the resist by depositing polysilicon, and it shall be evident that other materials than polysilicon can be used.

Next, the piezoelectric material 42 is filled in the open area 32 (S130). For that, processes shown in FIGS. 4 and 5 can be used. That is, as shown in FIG. 4, a piezoelectric material 40 can be deposited in the open area 32 and over the resist 30 by using a sputtering process or E-beam process, and then a portion of the deposited piezoelectric material 40 can be removed such that an upper surface of the resist 30 is exposed, as shown in FIG. 5. A CMP process can be used for removing a portion of the deposited piezoelectric material 40.

Then, an upper electrode 50 is selectively coated over the piezoelectric material 42 (S140). For that, processes shown in FIGS. 6 and 7 can be used. That is, a resist 52 can be formed such that a portion of the upper surface of the piezoelectric material 42 is opened—the opened area is an area where the upper electrode 50 is to be formed—and the upper electrode 50 can be deposited in the opened area by using, for example, a sputtering process, as shown in FIG. 6. Then, the upper electrode 50 can be patterned by removing the resist 52, as shown in FIG. 7.

Then, the resist 30 is removed, as shown in FIG. 8 (S150). That is, the resist 30 utilized for selectively depositing the piezoelectric material is removed.

If polysilicon is used for the resist 30 as described above, the resist 30 can be removed by an etching process using XeF₂ gas. In that case, the resist 30 can be selectively removed without damaging the head body 10 or the piezoelectric material 42. If any material other than polysilicon is used for the resist 30, an etching process using a material that can selectively remove the resist 30 without damaging the head body 10 or the piezoelectric material 42 can be used.

After the resist 30 is removed, an inlet port 17 is formed in the head body 10 (S160). For that, a process shown in FIGS. 9 to 11 can be used. That is, a resist 60 may be formed such that a portion of the head body 10 where the inlet port 17 is to be formed is opened, as shown in FIG. 9. And the opened portion of the head body 10 can be etched, as shown in FIG. 10. Then, the resist 60 may be removed, as shown in FIG. 11.

Meanwhile, processes shown in FIGS. 12 and 13 can be used for selectively coating the upper electrode 50, in another embodiment of the invention. That is, a conductive layer 54 can be coated over the piezoelectric material 42 and the resist 30. Here, the resist 30 is a photo-resist. Then, a portion of the conductive layer 54 formed on the photo-resist 30 can be removed by etching the photo-resist 30.

When the conductive layer 54 is coated over the upper surface of the piezoelectric material 42 and the photo-resist 30, and when the photo-resist 30 is etched selectively, a portion of the conductive layer 54 coated over the photo-resist 30 can be separated and removed. That is, the upper electrode 50 is patterned by a lift-off process.

Here, since the reactivity of the photo-resist 30 is different from those of the piezoelectric material 42, the lower electrode 20 and the conductive layer 54, the photo-resist 30 can be etched selectively without damaging the piezoelectric material 42, the lower electrode 20 or the conductive layer 54. As a result, only a portion of the conductive layer 54 coated over the piezoelectric material 42 can remain, and the remaining portion 50 of the conductive layer 54 can be patterned to serve as an upper electrode.

After the upper electrode 50 is patterned, the inlet port 17 can be formed in the head body 10.

While the spirit of the invention has been described in detail with reference to particular embodiments, the embodiments are for illustrative purposes only and do not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention. 

1. A method for manufacturing an inkjet head, the method comprising: preparing a head body including a vibrating membrane, the vibrating membrane located in an upper portion of the head body; coating a lower electrode over the vibrating membrane; patterning a resist such that an open area is formed on an upper side of the vibrating membrane; filling a piezoelectric material in the open area; selectively coating an upper electrode over the piezoelectric material; and removing the resist.
 2. The method of claim 1, wherein the resist is made of a material including polysilicon, and the removing of the resist is carried out by an etching process using XeF₂ gas.
 3. The method of claim 1, further comprising forming an inlet port in the head body, after the removing of the resist.
 4. The method of claim 1, wherein the filling of a piezoelectric material comprises: depositing the piezoelectric material in the open area and over the resist; and removing a portion of the deposited piezoelectric material such that an upper surface of the resist is exposed.
 5. The method of claim 1, wherein the resist is a photo-resist, and the selectively coating of an upper electrode comprises: coating a conductive layer over the piezoelectric material and over the photo-resist; and patterning the upper electrode over the piezoelectric material by removing a portion of the conductive layer coated over the photo-resist by etching the photo-resist. 